This invention pertains generally to pyrotechnic systems and more particularly to systems in which an ignitive reaction or shock wave is transmitted to a relatively movable body such as an airbag mounted on an automotive steering wheel.
Pyrotechnically fired airbags have recently been developed as an alternative to earlier systems in which inflation of an airbag was initiated by the firing of an electrically actuated squib. Instead of electrical impact sensors and electrical conductors interconnecting the sensors and squib, a pryotechnic system utilizes a mechanical sensor which fires a percussion primer and a shock tube or pyrotechnic transmission line for transmitting the ignitive reaction or percussive wave from the primer to the gas generator associated with the airbag. Pyrotechnic systems have certain advantages over electrical airbag systems in that they operate independently of electrical power sources and cannot be fired inadvertently by electrical disturbance or electromagnetic radiation. Moreover, a pryotechnic system provides long term reliability, requires very little maintenance and is relatively safe to manufacture and install since there is no electric squib to be fired inadvertently.
One problem with a pryotechnic system such as an airbag system is the difficulty of coupling the ignitive reaction or shock wave between a relatively stationary portion of the system and a relatively movable portion such as an airbag and gas generator mounted on the steering wheel. One prior art system uses a length of shock-tube cord or transmission line wrapped about the steering wheel hub and a detonator mounted on the steering column for igniting the cord.